Among the many insecticidal compounds, the phthalimidiothiophosphates have reached a relatively high degree of commercial success. These compounds are toxic to a large number of insect pests at different concentrations varying with the resistance of the insects mentioned. Some of these compounds are described in U.S. Pat. No. 2,767,194, specifically N-(mercaptomethyl) phthalimide-S-(O,O-dimethylphosphorodithioate).
The endeavor to extend the usefulness of the thiophosphates by increasing their effectiveness and lowering the cost has led to extensive studies on another class of biologically active chemicals, customarily referred to as synergists. Among the many synergists employed, the alkyl oxides, specifically, piperonyl butoxide, have been widely used. These compounds are described in U.S. Pat. No. 2,485,681 and 2,550,737.